Light metal pistons for internal combustion engines



July 12, 1938., E. w. SCHNEIDER I LIGHT METAL PISTONS FOR INTERNALCOMBUSTION ENGINES Filed Jan. 22, 1956 Patented July 1 2, 1938 men'sMETAL PISTONS Foa manual.

. COMBUSTION enemas Ernst Walter Schneider, Berlin, Germany ApplicationJanuary 22, 19:6, Serial No. 60,212 In Germany January 28, 1935 lclaim.

My invention relates to cast light metal pistons for internalcombustionengines comprising an upper head portion having a side walladapted to carry the piston rings and a lower skirt portion havingpiston pin bosses, said head portion and said skirt portion beingseparated by a circumferentially extending air gap and being integrallyconnected together by opposed thick webs, in vertical alignment withsaid piston pin bosses, depending from said head and being joined tosaid piston pin bosses.

In the light metal pistons already known, this connection is effected intwo different manners.

According to the first manner the piston cover and the two bosses areintegrally connected by means of intermediate webs the breadth of whichis equal to or somewhat greater than the diameter of the bosses.According to the second manner the'connection is made by an internalhollow cylinder coaxial with the piston mantle.

The first manner of connection did not prove a good one because, due tothe irregular distribution of the masses, the heat as well as thepressures were not transferred uniformly and consequently, deformationsof the piston mantle and wear and tear of the piston were caused.

In the second manner of connection, by means of an internal hollowcylinder, these disadvantages are partly removed but there arises thefollowing disadvantage: The piston'cover is not uniformly heated butheated most along that annular portion which 11% in alignment with theinternal hollow cylinder because at the circumference of the pistoncover the heat is lead of! by the wall of the cylinder while in themiddle of the piston cover the heat is lead off by the oil sprayedagainst the piston cover when the motor is running. The internal hollowcylinder attached to said hot annular portion of the piston cover isrelatively hot and lengthened to a correspondingly great amount. By theforces arising thereby both the piston cover and, by the intermediary ofthe bosses, the lower skirt portion of the piston are deformed. Besides,the

45 manufacturing of such pistons by means of chill- (coci1l castingpresents considerable dlfllculty.

The internal hollow cylinder must be separated from the piston skirt onits entire circumference by an annular sir space. On a great part of the50 circumference, the core for forming this air space can be combinedwith, or can form part of the core for forming the piston skirt.However, those two parts of the annular air space which lie ,above thebosses mustbe provided for during the 55 casting by means of specialcore-parts which must afterwards be rotated and drawn out. Such a chill(cocill) device is complicated and the manufacturing costs of the pistonare increased. The invention relates to light metal pistonsmadeaccording to the second manner and. has 5 for'its object to avoidthe above-named disad vantages. In the light metal pistons constructedaccording to my invention, no deforming forces are produced by theheating of the parts. The. piston retains on its entire length itsaccurate m cylindrical form, even with the highest tem- 'peraturesoccuring during theworking of the motor. Therefore, the piston: can befinished into its accurate cylindrical form in. contrast with the usualpistons which must intentionally be deformed during the manufacturing inorder to equalize the deformations eflectedby the heat both at thecircumference-of the piston cover and at the outer surfaces of thebosses. The cost of the manufacturing of the new piston is dimin- 20ishd furthermore in that the piston can be cast in chills (cocills) in asimple manner and espe-' cially in that core-parts are avoided whichafterwards must be drawn out. The manufacturing costsare diminishedfurthermore by the dimin- 25 ishing of the weight attained in myinvention;

The present invention has for its object a piston of the first describedtype and comprising additional thin webs intermediate said thick webs,said thin webs depending also from said 30 head and being joined to saidpiston pin bosses and being furthermore spaced inwardly from the sidewall of said head, and a preformed metallic segment disposed in each ofsaid thick webs, each of said segments having a lug extending inwardlytherefrom and through a thick web, said metallic segments being spacedat least in part from the adjacent cast metal of the piston by spacesresulting from the shrinkage of said metal in cooling. By theseshrinking spaces and by the air spaces which are provided for in thecasting directly by the core, an uninterrupted annular heat insulatingair gap is formed surrounding I the internal hollow cylinder on allsides. On each of the two preformed metallic segments there are fixedone or several radially inwardly directed lugs or webs around which,during the cooling of the casting, likewise shrinking spaces are formedBy the shrinking spaces surrounding the lugs the internal hollowcylinder is subdivided, in the very thick parts of the hollow cylinderlying above the bosses. By this subdivision of the internal hollowcylinder great tensions are completely avoided, which would appear ifthe hollow cylinder'be a closed one, since the shrinking spaces aresuflicient to receive the linear ex'- tensions of the wall of theinternal-hollow cylinder. Since in the piston according to my inventionsuch extension forces do not exist and, therefore, forces and pressures,to be transferred by the hollow cylinder to the bosses, cannot takeplace, the dimensions of the hollow cylinder have to correspond only tothe operating stresses. Hereby and by the diminution of the thickness 10of the wall of the piston skirt rendered possible 'by the fact thatdeformations of the, skirt are avoided and, therefore, the originalaccurately cylindrical form is maintained, the weight of the piston isreduced to a considerable 'degree. That 15 is besides the reduction ofthe costs of extreme importance for the rapidly rotating motors withregard to the great accelerating forces.

In order that the invention may be more fully understood reference willbe had to the accom- 20 p'anying drawing in which Fig. .1 is a verticallongitudinal sectional view of the piston on the line il of Fig. 3;

Fig. 2 is a vertical longitudinal sectional view on the line 2-2 of Fig.3; 25 Fig. 3 is a transverse horizontal sectional view on the line 3-3of Fig. 1;

Fig. 4 is a transverse horizontal sectional view on the line 4-4 of Fig.1;

Figs. 5a-5 show a metal enclosure in plan 30 view and vertical view;

Figs. 6a6 show a modified metal enclosure in plan view and verticalview.

The light metal piston shown in the drawing is cast as a whole in thechill (cocill). a is the 35 piston cover b, b are the two piston pinbosses by which the piston is pivoted to the connecting rod. The pistonskirt consists of the lower skirt portion and the upper head portioncprovided with the grooves into which the piston rings are to 40 beinserted. During the casting the portions 0 and c are integrallyconnected. They are sep-- arated afterwards by an annular groove e cutinto the mantle. The bosses, b, b are connected with the piston cover aby an internal hollow cylinder separated on its entire circumferencefrom the piston mantle c c by an insulating air gap. This hollowcylinder consists of two portions of greater thickness continuing thebosses upwardly, and to be separated during the casting from the skirtportion c by air gaps in a manner to be described afterwards, and f twohollow cylinder portions 27', b ofless t .kness between which and themantle portion 0 ring sector formed air spaces m, m (see Figs. 2 and 3)are provided dur- 55 ing the casting. The separation and insulation ofthe portions b from the mantle part c are eflected by insertingpreformed metallic segments 41 provided with radial lugs i. The metallicsegments remain in the casting. During the cooling on of the castingthere are formed, the so-called shrinking spaces. By the shrinkingspaces k lying near the external cylindrical surfaces and by theshrinking spacesk lying near the internal cylindrical surfaces of thesegments, the portions b of the internal hollow cylinder are separatedfrom the mantle part c. By these shrinking spaces in combination withthe above-mentioned ring-sector-formed air spaces 11:, m there isprovided a space entirely surrounding the hollow cylinder b I), b b. Bythe shrinking spaces k, k is", is adjacent to the two sides of the lugs1' each of the two thickened portions b 11 is subdivided into two partsseparated one from another by air gaps, The air gaps are great enough toreceive the linear extension of the hollow cylinder b b b b caused bythe heating and thereby to prevent the generation of tension forces inthe hollow cylinder and of deformations of the piston cover and themantle- The heat transferred from the piston cover a to the hollowcylinder b b b b is transferred from the hollow cylinder to the bossesb, b and from the bosses partly to the wrist pin and the connecting rod,and partly to the skirt portion 0 For reducing the heat transferred tothe piston skirt the material connecting the bearing 1) with the skirtportion c may be reduced by providing wedgeshaped spaces I on each sideof each of the two bosses. The wedge-shaped spaces may partly cut thebores b of the bosses b so that oil grooves are formed.

Instead of metallic segments having smooth cylindrical surfaces and asingle radial lug, as

shown in Figs. 1, 2, 3, and 5 metallic segments can be used formed byundulated sheets and/or provided with several radial lugs. An undulatedmetal segment provided with two radial lugs is shown in Fig. 6 in planview and vertical view.

My invention is not limited to the particular form of the pistondescribed but may be variously modified without departing from thespiritan scope of my invention. a

What I claim is: A cast light metal piston for internal combustionengines comprising an upper head portion V having a side wall adapted tocarry piston rings, and a lower skirt portion having piston pin bosses,said head portion and said skirt portion being separated by acircumferentially extending air gap and being integrally connectedtogether by each of said thick webs, each of said segments having a lugextending inwardly therefrom and through a thick web, said metallicsegments being spaced at least in part from the adjacent cast metal ofthe piston by spaces resulting from the shrinkage of said metal incooling.

ERNST WALTER SCHNEIDER.

